Obesity and systemic oxidative stress: clinical correlates of oxidative stress in the Framingham Study

OBJECTIVE

To determine the clinical conditions associated with systemic oxidative stress in a community-based cohort. Information regarding cardiovascular risk factors associated with systemic oxidative stress has largely been derived from highly selected samples with advanced stages of vascular disease. Thus, it has been difficult to evaluate the relative contribution of each cardiovascular risk factor to systemic oxidative stress and to determine whether such risk factors act independently and are applicable to the general population.

METHODS AND RESULTS

We examined 2828 subjects from the Framingham Heart Study and measured urinary creatinine-indexed levels of 8-epi-PGF2alpha as a marker of systemic oxidative stress. Age- and sex-adjusted multivariable regression models were used to assess clinical correlates of oxidative stress. In age- and sex-adjusted models, increased urinary creatinine-indexed 8-epi-PGF2alpha levels were positively associated with female sex, hypertension treatment, smoking, diabetes, blood glucose, body mass index, and a history of cardiovascular disease. In contrast, age and total cholesterol were negatively correlated with urinary creatinine-indexed 8-epi-PGF2alpha levels. After adjustment for several covariates, decreasing age and total/HDL cholesterol ratio, sex, smoking, body mass index, blood glucose, and cardiovascular disease remained associated with urinary 8-epi-PGF2alpha levels.

CONCLUSIONS

Smoking, diabetes, and body mass index were highly associated with systemic oxidative stress as determined by creatinine-indexed urinary 8-epi-PGF2alpha levels. The effect of body mass index was minimally affected by blood glucose, and diabetes and may suggest an important role of oxidative stress in the deleterious impact of obesity on cardiovascular disease.

Platelet activation in obese women: role of inflammation and oxidant stress

CONTEXT

Obesity, in particular abdominal adiposity, is associated with increased cardiovascular morbidity and mortality through mechanisms possibly linking the metabolic disorder to platelet and vascular abnormalities.

OBJECTIVE

To investigate the clinical and biochemical determinants of lipid peroxidation and platelet activation in obese women.

DESIGN, SETTING, AND PARTICIPANTS

Cross-sectional comparison, conducted between September 1999 and September 2001, of urinary 8-iso prostaglandin F(2alpha) (8-iso PGF(2alpha)) and 11-dehydrothromboxane B2 (11-dehyhdro-TxB2) excretion levels in 93 women: 44 with a body mass index (BMI) higher than 28 and a waist-to-hip ratio (WHR) of 0.86 or higher, android obesity; 25 with a BMI higher than 28 and a WHR lower than 0.86, gynoid obesity; and 24 nonobese women with a BMI lower than 25. An additional study was conducted to determine the short-term effects of weight loss in 20 of the 44 women with android obesity.

INTERVENTION

During a 12-week period, 20 women with android obesity followed a weight loss program to reduce caloric intake to about 1200 kcal/d.

MAIN OUTCOME MEASURES

Plasma C-reactive protein, insulin and leptin levels, and urinary 8-iso PGF(2alpha) (marker of in vivo lipid peroxidation) and 11-dehyhdro-TxB2 (marker of in vivo platelet activation) excretion. Weight loss was defined as successful when the initial body weight decreased by at least 5 kg after a 12-week period of caloric restriction.

RESULTS

Women with android obesity had higher levels of 8-iso PGF(2alpha )(median [interquartile range [IQR]] 523 [393-685] vs 187 [140-225] pg/mg creatinine) and 11-dehyhdro-TxB2 (median [IQR], 948 [729-1296] vs 215 [184-253] pg/mg creatinine) than nonobese women (P<.001). Both 8-iso PGF(2alpha)and 11-dehyhdro-TxB2 were higher in women with android obesity than women with gynoid obesity (P<.001). Based on multiple regression analysis, C-reactive protein levels and WHRs of 0.86 or higher predicted the rate of 8-iso PGF(2alpha) excretion independently of insulin and leptin levels. Of 20 women with android obesity, 11 achieved successful weight loss, which was associated with statistically significant reductions in C-reactive protein (median change, 23%; P<.05), 8-iso PGF(2alpha) (median change, 32%; P =.04) and 11-dehydro-TxB2 (median change, 54%; P =.005).

CONCLUSIONS

Android obesity is associated with enhanced lipid peroxidation and persistent platelet activation. These abnormalities are driven by inflammatory triggers related to the degree of abdominal adiposity and are, at least in part, reversible with a successful weight-loss program.

Association between oxidative stress and bone mineral density

Free radicals have been shown to be involved in bone resorption in vitro and in rodents. We studied the effect of oxidative stress on bone mineral density (BMD) in 48 women and 53 men from a population-based study. The levels of 8-iso-PGF(2alpha) (a major F(2)-isoprostane and a biomarker of oxidative stress) and a control, 15-keto-dihydro-PGF(2alpha) (a biomarker of inflammatory response), were measured in urinary samples and their association with BMD and quantitative ultrasound (QUS) measurements were examined. In multivariate linear regression analyses, 8-iso-PGF(2alpha) levels were negatively associated with both BMD and QUS. In contrast, no association was found for 15-keto-dihydro-PGF(2alpha). Our findings establish a biochemical link between increased oxidative stress and reduced bone density and provide a rational for further studies investigating the role of pro- and antioxidants in osteoporosis.

Fruit and vegetable consumption and its relation to markers of inflammation and oxidative stress in adolescents

BACKGROUND

Fruits and vegetables, foods rich in flavonoids and antioxidants, have been associated with lower risk of stroke, coronary heart disease, and markers of inflammation and oxidative stress in adults. Markers of inflammation and oxidative stress are predictors of coronary heart disease risk; however, it is unknown whether these markers are related to dietary flavonoid and antioxidant intake in youth.

OBJECTIVE

To determine whether greater intakes of fruit and vegetables, antioxidants, folate, and total flavonoids were inversely associated with markers of inflammation and oxidative stress in 285 adolescent boys and girls aged 13 to 17 years.

DESIGN

In this cross-sectional study conducted between February 1996 and January 2000, diet was assessed by a 127-item food frequency questionnaire. Height and weight measurements were obtained and a fasting blood sample drawn. Spearman partial correlation analyses evaluated the relation of intakes of fruit and vegetables, antioxidants, folate, and flavonoids with markers of inflammation (C-reactive protein, interleukin-6, tumor necrosis factor-alpha, and 15-keto-dihydro-PGF(2alpha) metabolite and oxidative stress (urinary 8-iso prostaglandin F(2alpha), an F(2)-isoprostane), adjusting for age, sex, race, Tanner stage, energy intake, and body mass index.

RESULTS

Urinary F(2)-isoprostane was inversely correlated with intakes of total fruit and vegetables, vitamin C, beta carotene, and flavonoids. Serum C-reactive protein was significantly inversely associated with intakes of fruit (r=-0.19; P=0.004), vitamin C (r=-0.13, P=0.03), and folate (r=-0.18; P=0.004). Serum interleukin-6 was inversely associated with intakes of legumes, vegetables, beta carotene, and vitamin C. Serum tumor necrosis factor-alpha was inversely associated with beta carotene (r=-0.14, P=0.02) and luteolin (r=-0.15, P=0.02).

CONCLUSION

Study results show that the beneficial effects of fruit and vegetable intake on markers of inflammation and oxidative stress are already present by early adolescence and provide support for the Dietary Guidelines for Americans "to consume five or more servings per day" of fruits and vegetables to promote beneficial cardiovascular health.

Bioconversion of vaccenic acid to conjugated linoleic acid in humans

BACKGROUND

Vaccenic acid (11-trans octadecenoic acid; VA), a major trans fatty acid in the fat of ruminants, is produced in the rumen and converted in tissues to rumenic acid (9-cis, 11-trans octadecenoic acid; RA), an isomer of conjugated linoleic acid, by Delta(9)-desaturase. There are indications that this conversion also occurs in humans.

OBJECTIVE

The aim of this controlled intervention was to study the conversion of VA to RA in humans after consumption of diets with increasing amounts of VA.

DESIGN

Thirty healthy subjects consumed a baseline diet rich in oleic acid for 2 wk. The subjects were then divided into 3 groups (n = 10 per group) and provided a diet containing 1.5, 3.0, or 4.5 g VA/d for 9 d. All diets contained equal amounts of macronutrients and differed only in their fatty acid compositions. The fats were mixed into conventional foods, and nearly all food was provided during the study.

RESULTS

The proportion of VA in serum total fatty acids increased 94%, 307%, and 620% above baseline with the 1.5-, 3.0-, and 4.5-g diets, respectively. This was associated with a linear increase in the proportion of RA. The conversion rate was 19% on average, with significant interindividual differences with all 3 intakes of VA. The urinary excretion of 8-iso-prostaglandin F(2alpha) increased in all groups (P < 0.001).

CONCLUSIONS

The results quantify the desaturation of VA to RA in humans. Conversion is likely to contribute significantly to the amount of RA available to the body, and dietary intakes of VA should thus be taken into account when predicting RA status.

Greater oxidative stress in healthy young men compared with premenopausal women

Coronary risk factors, including age, hypertension, diabetes mellitus, hyperlipidemia, and smoking, are associated with enhanced oxidative stress, which is implicated as a potential mechanism for atherogenesis and atherosclerotic cardiovascular diseases. Male sex is one of the well-known cardiovascular risk factors. We tested the hypothesis that oxidative stress is greater in men than in women. Plasma thiobarbituric acid-reactive substances (TBARS) and urinary 8-isoprostaglandin F2alpha (8-iso-PGF2alpha) were measured in 52 young men and 51 age-matched women. The subjects were healthy, were not smokers, and were not taking any medications or vitamins. Age, blood pressure, plasma cholesterol, and glucose did not differ between the groups. Baseline TBARS (2.32 +/- 0.11 [men] versus 1.87 +/- 0.09 [women] nmol/mL, P<0.01) and 8-iso-PGF2alpha (292 +/- 56 [men] versus 164 +/- 25 [women] pg/mg creatinine, P<0.05) were higher in men than in women. Supplementation of antioxidant vitamins for 4 weeks in men produced a significant reduction in TBARS and 8-iso-PGF2alpha by 34% (P<0.01) and 48% (P<0.05), respectively. Plasma superoxide dismutase, catalase, and vitamin E levels were comparable between the groups. Enhanced oxidative stress in men may provide a biochemical link between male sex and atherosclerotic diseases related to oxidative stress.

Effect of eicosapentaenoic acid and docosahexaenoic acid on oxidative stress and inflammatory markers in treated-hypertensive type 2 diabetic subjects

n-3 fatty acids reduce the risk of cardiovascular disease via a number of possible mechanisms. Despite this, there has been concern that these fatty acids may increase lipid peroxidation. The data in vivo are inconclusive, due in part to limitations in the methodologies. In this regard, the measurement of F2-isoprostanes provides a reliable assessment of in vivo lipid peroxidation and oxidant stress. This study aimed to assess the effects of supplementation with purified eicosapentaenoic acid (EPA) or docosahexaenoic acid (DHA), the two major n-3 fatty acids, on urinary F2-isoprostanes and markers of inflammation, in type 2 diabetic patients. In a double-blind, placebo controlled trial of parallel design, 59 nonsmoking, treated-hypertensive, type 2 diabetic subjects, were randomized to 4 g daily of purified EPA, DHA, or olive oil for 6 weeks, while maintaining their usual diet. F2-isoprostanes, measured using gas chromatography-mass spectrometry in 24 h urines and C-reactive protein (CRP), interleukin-6 (IL-6) and tumor necrosis factor-alpha (TNF-alpha), were measured before and after intervention. Thirty-nine men and 12 women aged 61.2 +/- 1.2 years, with body mass index (BMI), 29.5 +/- 0.5 kg/m2; 24 h blood pressure, 138/73 mmHg; HbA1c, 7.3 +/- 0.1% and fasting glucose, 7.9 +/- 0.2 mmol/l completed the intervention. Baseline urinary F2-isoprostanes were positively associated with HbA1c (p=.011) and fasting glucose (p=.032). Relative to the olive oil group, postintervention urinary F2-isoprostanes were decreased 19% by EPA (p=.017) and 20% by DHA (p=.014). There were no significant changes in CRP, IL-6, and TNF-alpha following EPA or DHA supplementation. In regression analysis, Delta F2-isoprostanes were positively associated with Delta HbA1c (p=.007) independent of treatment group; and with Delta TNF-alpha (p=.034) independent of age, gender, BMI, and treatment group. There were no associations with Delta CRP or Delta IL-6. This study is the first report demonstrating that either EPA or DHA reduce in vivo oxidant stress without changing markers of inflammation, in treated hypertensive, type 2 diabetic subjects.

Effect of diet and exercise intervention on blood pressure, insulin, oxidative stress, and nitric oxide availability

BACKGROUND

Diet and exercise can affect blood pressure and atherosclerotic risk.

METHODS AND RESULTS

The present study was designed to examine the effects of a short-term, rigorous diet and exercise intervention on blood pressure, hyperinsulinemia, and nitric oxide (NO) availability. Men (n=11) were placed on a low-fat, high-fiber diet combined with daily exercise for 45 to 60 minutes for 3 weeks. Pre- and post fasting blood was drawn for serum lipid, insulin, 8-isoprostaglandin F(2alpha) (8-iso-PGF(2alpha)), and glucose measurements. Anthropometric parameters, blood pressure (BP), and 24-hour urinary NO metabolite excretion (NO(X)), a marker of NO bioavailability, were measured. Systolic (P<0.01) and diastolic BP (P<0.01) and 8-iso-PGF(2alpha) decreased (P<0.05), whereas urinary NO(X) increased (P<0.05). There was a significant reduction in fasting insulin (P<0.01) and a significant correlation between the decrease in serum insulin and the increase in urinary NO(X) (r2=0.68, P<0.05). All fasting lipids decreased significantly, and the total cholesterol to high-density lipoprotein cholesterol ratio improved. Although body weight and body mass index (P<0.01) decreased, obesity was still present and there were no correlations between the change in body mass index and the change in insulin, BP, or urinary NO(X).

CONCLUSIONS

This intervention resulted in dramatic improvements in BP, oxidative stress, NO availability, and the metabolic profile within 3 weeks, mitigating the risk for atherosclerosis progression and its clinical sequelae.

A mouse model of angiotensin II slow pressor response: role of oxidative stress

ABSTRACT. The slow pressor response to prolonged infusions of angiotensin II (AngII) entails a delayed rise in BP. This study investigated the hypothesis that the response depends on the generation of oxidative stress. The BP and renal functional response of mice to graded doses (200, 400, and 1000 ng. kg(-1). min(-1)) of subcutaneously infused AngII was studied. The SBP of conscious mice increased by day 3 at AngII1000 but showed a delayed rise by days 9 to 13 (slow pressor response) at the lower rates of AngII infusion. By day 13, there was a graded increase in SBP with the rate of AngII infusion (Vehicle, -2.6 +/- 2.6%; AngII200, +14.1 +/- 5.0%; AngII400, +31.9 +/- 1.9%; AngII1000, +43.2 +/- 5.5%). The MAP measured under anesthesia rose significantly (P < 0.001) with AngII400 at 14 d (Vehicle, 85 +/- 2 mmHg; AngII400, 100 +/- 3 mmHg). When studied at day 6, the MAP of AngII400 rats was not elevated (88 +/- 2 mmHg; NS versus vehicle), yet the GFR was higher (1.05 +/- 0.05 versus 1.25 +/- 0.05 ml. min(-1). g(-1); P < 0.05) accompanied by an increase in the filtration fraction (FF) (28.8 +/- 1.2 versus 37.2 +/- 0.8%; P < 0.001). From day 6 through day 14, the MAP had increased (P < 0.01) in AngII400, accompanied by a significant reduction in GFR to 1.05 +/- 0.04 ml. min(-1). g(-1) (P < 0.01) and elevation of renal vascular resistance (RVR) (day 6 versus day 14, 15.3 +/- 0.6 versus 19.2 +/- 1.2 mmHg. ml(-1). min(-1). g(-1); P < 0.05). Renal excretion of 8-iso PGF(2alpha) was increased in AngII400 group at day 12 (2.52 +/- 0.35 versus 5.85 +/- 0.78 pg. day(-1); P < 0.01). The permeant superoxide dismutase mimetic tempol reduced the effects of AngII400 on the SBP (-1.7 +/- 5.8%; P < 0.01), the MAP (87 +/- 4 mmHg; P < 0.01), and the RVR (15.2 +/- 0.5 mmHg. ml(-1). min(-1). g(-1); P < 0.05) at day 14 and the renal 8-iso PGF(2alpha) excretion (3.53 +/- 0.71 pg. d(-1); P < 0.05) at day 12. It is concluded that the AngII infused mouse is a valid model for the slow pressor response. There is an early rise in GFR and FF, consistent with increased postglomerular vascular resistance and a late rise in RVR with a fall in GFR, consistent with increased preglomerular vascular resistance that is accompanied by a rise in BP. There is evidence of increased oxidative stress that is implicated in the increase in the BP and RVR in this model.

Increased oxidative stress and platelet activation in patients with hypertension and renovascular disease

BACKGROUND

Hypertensive patients with renovascular disease (RVD) may be exposed to increased oxidative stress, possibly related to activation of the renin-angiotensin system.

METHODS AND RESULTS

We measured the urinary excretion of 8-iso-prostaglandin (PG) F2alpha and 11-dehydro-thromboxane (TX) B2 as indexes of in vivo lipid peroxidation and platelet activation, respectively, in 25 patients with RVD, 25 patients with essential hypertension, and 25 healthy subjects. Plasma renin activity in peripheral and renal veins, angiotensin II in renal veins, cholesterol, glucose, triglycerides, homocysteine, and antioxidant vitamins A, C, and E were also determined. Patients were also studied 6 months after a technically successful angioplasty of the stenotic renal arteries. Urinary 8-iso-PGF2alpha was significantly higher in patients with RVD (median, 305 pg/mg creatinine; range, 124 to 1224 pg/mg creatinine) than in patients with essential hypertension (median, 176 pg/mg creatinine; range, 48 to 384 pg/mg creatinine) or in healthy subjects (median, 123 pg/mg creatinine; range, 58 to 385 pg/mg creatinine). Urinary 11-dehydro-TXB2 was also significantly higher in RVD patients compared with healthy subjects. In RVD patients, urinary 8-iso-PGF2alpha correlated with 11-dehydro-TXB2 (r(s)=0.48; P<0.05) and renal vein renin (r(s)=0.67; P<0.005) and angiotensin II (r(s)=0.65; P=0.005) ratios. A reduction in 8-iso-PGF2alpha after angioplasty was observed in RVD patients with high baseline levels of lipid peroxidation. Changes in 8-iso-PGF2alpha were related to baseline lipid peroxidation (r(s)=-0.73; P<0.001), renal vein angiotensin II (r(s)=-0.70; P<0.01) and renin (r(s)=-0.63; P<0.05) ratios.

CONCLUSIONS

Lipid peroxidation is markedly enhanced in hypertensive patients with RVD and is related to activation of the renin-angiotensin system. Moreover, persistent platelet activation triggered or amplified by bioactive isoprostanes may contribute to the progression of cardiovascular and renal damage in this setting.

Comparison of the antioxidant effects of Concord grape juice flavonoids alpha-tocopherol on markers of oxidative stress in healthy adults

BACKGROUND

Concord grape juice (CGJ) is a rich source of flavonoids, which have greater antioxidant efficacy in vitro than does alpha-tocopherol; however, the efficacies of flavonoids and alpha-tocopherol in vivo have not been compared.

OBJECTIVE

We compared the in vivo antioxidant efficacy of CGJ with that of alpha-tocopherol in healthy adults.

DESIGN

Subjects were randomly assigned to receive either 400 IU RRR-alpha-tocopherol/d (n = 17) or 10 mL CGJ. kg(-1). d(-1) (n = 15) for 2 wk. Serum oxygen radical absorbance capacity, plasma protein carbonyls, urinary F(2)-isoprostanes, and resistance of LDL to ex vivo oxidation were measured before and after supplementation as markers of antioxidant status and oxidative stress.

RESULTS

After supplementation, plasma alpha-tocopherol increased 92% in subjects who received alpha-tocopherol (P < 0.001); plasma total and conjugated phenols increased 17% (P < 0.01) and 22% (P < 0.001), respectively, in subjects who received CGJ. There was a significant change in plasma triacylglycerols in both groups, but the concentrations were within the normal range. CGJ supplementation was associated with significantly higher triacylglycerols than was alpha-tocopherol supplementation. Both supplementation regimens significantly increased serum oxygen radical absorbance capacity (P < 0.001) and LDL lag time (P < 0.001) and significantly decreased the LDL oxidation rate (P < 0.01), with no significant difference in effectiveness. Protein carbonyl concentrations in native plasma decreased 20% after CGJ supplementation, which was a significantly different response than that after alpha-tocopherol supplementation (P < 0.05).

CONCLUSIONS

In healthy adults, 10 mL CGJ. kg(-1). d(-1) increased serum antioxidant capacity and protected LDL against oxidation to an extent similar to that obtained with 400 IU alpha-tocopherol/d but decreased native plasma protein oxidation significantly more than did alpha-tocopherol. CGJ flavonoids are potent antioxidants that may protect against oxidative stress and reduce the risk of free radical damage and chronic diseases.

The Mediterranean diet improves the systemic lipid and DNA oxidative damage in metabolic syndrome individuals. A randomized, controlled, trial

BACKGROUND & AIMS

Metabolic syndrome (MetS), in which a non-classic feature is an increase in systemic oxidative biomarkers, presents a high risk of diabetes and cardiovascular disease (CVD). Adherence to the Mediterranean Diet (MedDiet) is associated with a reduced risk of MetS. However, the effect of the MedDiet on biomarkers for oxidative damage has not been assessed in MetS individuals. We have investigated the effect of the MedDiet on systemic oxidative biomarkers in MetS individuals.

METHODS

Randomized, controlled, parallel clinical trial in which 110 female with MetS, aged 55-80, were recruited into a large trial (PREDIMED Study) to test the efficacy of the traditional MedDiet on the primary prevention of CVD. Participants were assigned to a low-fat diet or two traditional MedDiets (MedDiet + virgin olive oil or MedDiet + nuts). Both MedDiet group participants received nutritional education and either free extra virgin olive oil for all the family (1 L/week), or free nuts (30 g/day). Diets were ad libitum. Changes in urine levels of F2-Isoprostane (F2-IP) and the DNA damage base 8-oxo-7,8-dihydro-2'-deoxyguanosine (8-oxo-dG) were evaluated at 1-year trial.

RESULTS

After 1-year urinary F2-IP decreased in all groups, the decrease in MedDiet groups reaching a borderline significance versus that of the Control group. Urinary 8-oxo-dG was also reduced in all groups, with a higher decrease in both MedDiet groups versus the Control one (P < 0.001).

CONCLUSIONS

MedDiet reduces oxidative damage to lipids and DNA in MetS individuals. Data from this study provide evidence to recommend the traditional MedDiet as a useful tool in the MetS management.

Consumption of whole grain and legume powder reduces insulin demand, lipid peroxidation, and plasma homocysteine concentrations in patients with coronary artery disease: randomized controlled clinical trial

Our objective was to evaluate whether isocaloric replacement of refined rice with whole grains and other plant products as a form of powder reduces coronary artery disease (CAD) risk factors, such as insulin demand and lipid peroxidation in CAD patients. Seventy-six male patients with CAD were randomly assigned to either a group ingesting a whole-grain meal daily or a control group for 16 weeks. In the whole-grain group, serum concentrations of glucose and insulin decreased by 24% and 14%, respectively, without altering body weight and energy intake, whereas daily intakes of fiber and vitamin E increased by 25% and 41%, respectively. Consumption of whole grains and legume powder in CAD patients without diabetes decreased fasting levels of glucose and insulin. The areas under the curve for insulin and glucose during the oral glucose tolerance test were also decreased. CAD patients with diabetes in the whole-grain group also showed reductions in fasting glucose and in the area under the curve for glucose. In the whole-grain group, plasma malondialdehyde and homocysteine and urinary 8-epi-prostaglandin F(2alpha) concentrations decreased by approximately 28%. Also, lipid-corrected concentrations of alpha-carotene, retinol, tocopherols, and lycopene increased by 11% to 40%, and the percentage composition of n-6 fatty acids of serum phospholipid increased by 14% in the whole-grain group. The replacement of refined rice with whole grain and legume powder as a source of carbohydrate in a meal showed significant beneficial effects on glucose, insulin, and homocysteine concentrations and lipid peroxidation in CAD patients. These effects are likely to substantially reduce the risk factors for CAD and diabetes.

Effects of vitamin C and vitamin E on in vivo lipid peroxidation: results of a randomized controlled trial

BACKGROUND

Lipid peroxidation may be important in the pathogenesis of atherosclerosis, particularly in its earliest stages. Evidence predominantly from in vitro studies suggests that antioxidant vitamins can prevent lipid peroxidation and that vitamin C and vitamin E have synergistic effects. However, in vivo evidence in support of these hypotheses is sparse.

OBJECTIVE

The objective was to determine the effects of vitamin C and vitamin E, alone or in combination, on in vivo lipid peroxidation.

DESIGN

We conducted a placebo-controlled, 2 x 2 factorial trial of vitamin C (500 mg ascorbate/d) and vitamin E (400 IU RRR-alpha-tocopheryl acetate/d) supplementation in 184 nonsmokers. The mean duration of supplementation was 2 mo. The outcome measures were changes from baseline in urinary 8-iso-prostaglandin F(2alpha), urinary malondialdehyde + 4-hydroxyalkenals, and serum oxygen-radical absorbance capacity.

RESULTS

The within-group mean changes (and 95% CIs) in urinary 8-iso-prostaglandin F(2alpha) (pg/mg creatinine) were 9.0 (-125.1, 143.1), -150.0 (-275.4, -24.6), -141.3 (-230.5, -52.1), and -112.5 (-234.8, 9.8) in the placebo, vitamin C alone, vitamin E alone, and vitamins C + E groups, respectively. No synergistic effect of these 2 vitamins on urinary 8-iso-prostaglandin F(2alpha) was observed (P = 0.12). Neither vitamin had an effect on urinary malondialdehyde + 4-hydroxyalkenals. Vitamin C, but not vitamin E, increased serum oxygen-radical absorbance capacity (P = 0.01).

CONCLUSIONS

Supplementation with vitamin C or vitamin E alone reduced lipid peroxidation to a similar extent. Supplementation with a combination of vitamins C and E conferred no benefit beyond that of either vitamin alone.

Increased Oxidative Stress Following Acute and Chronic High Altitude Exposure

The generation of reactive oxygen species is typically associated with hyperoxia and ischemia reperfusion. Recent evidence has suggested that increased oxidative stress may occur with hypoxia. We hypothesized that oxidative stress would be increased in subjects exposed to high altitude hypoxia. We studied 28 control subjects living in Lima, Peru (sea level), at baseline and following 48 h exposure to high altitude (4300 m). To assess the effects of chronic altitude exposure, we studied 25 adult males resident in Cerro de Pasco, Peru (altitude 4300 m). We also studied 27 subjects living in Cerro de Pasco who develop excessive erythrocytosis (hematocrit > 65%) and chronic mountain sickness. Acute high altitude exposure led to increased urinary F(2)-isoprostane, 8-iso PGF(2 alpha) (1.31 +/- 0.8 microg/g creatinine versus 2.15 +/- 1.1, p = 0.001) and plasma total glutathione (1.29 +/- 0.10 micromol versus 1.37 +/- 0.09, p = 0.002), with a trend to increased plasma thiobarbituric acid reactive substance (TBARS) (59.7 +/- 36 pmol/mg protein versus 63.8 +/- 27, p = NS). High altitude residents had significantly elevated levels of urinary 8-iso PGF(2 alpha) (1.3 +/- 0.8 microg/g creatinine versus 4.1 +/- 3.4, p = 0.007), plasma TBARS (59.7 +/- 36 pmol/mg protein versus 85 +/- 28, p = 0.008), and plasma total glutathione (1.29 +/- 0.10 micromol versus 1.55 +/- 0.19, p < 0.0001) compared to sea level. High altitude residents with excessive erythrocytosis had higher levels of oxidative stress compared to high altitude residents with normal hematological adaptation. In conclusion, oxidative stress is increased following both acute exposure to high altitude without exercise and with chronic residence at high altitude.

Oxidant stress is a significant feature of primary biliary cirrhosis

Primary biliary cirrhosis (PBC) is a chronic cholestatic disorder characterised by an immunological, and often granulomatous, attack on bile ducts leading to fibrosis, cirrhosis, liver failure and death. Animal and human studies suggest that oxidant stress plays a key role in progression of other liver diseases, but no comprehensive investigation has been performed previously in PBC. A wide range of lipid peroxidation and antioxidant markers were measured in the blood and urine of 41 patients with histologically confirmed PBC. Lipid peroxidation markers were significantly elevated [plasma and urinary 8-isoprostane, P<0.001; plasma malondialdehyde (MDA), P=0.007] compared to age- and sex-matched controls. The most striking antioxidant depletion occurred with plasma total glutathione where levels were significantly reduced (30% of controls). Total serum antioxidant levels were decreased (P=0.013) and serum selenium and vitamin A were also lower (both P<0.001); vitamins C and E were normal. Most patients had early disease biochemically and were Child-Pugh grade A. Urinary 8-isoprostane correlated positively with Ludwig stage and markers of hepatic injury and cholestasis. This study clearly demonstrates that oxidant stress, as reflected in a comprehensive spectrum of lipid peroxidation and antioxidant markers, is a significant feature of early-stage PBC.

Enhanced lipid peroxidation and platelet activation in the early phase of type 1 diabetes mellitus: role of interleukin-6 and disease duration

BACKGROUND

To investigate early events possibly related to the development of diabetic angiopathy, we examined whether 8-iso-prostaglandin F2alpha (8-iso-PGF2alpha) formation, a marker of in vivo oxidant stress, is altered in different stages of type 1 diabetes (T1DM) and whether it correlates with the rate of thromboxane (TX) A2 biosynthesis, a marker of in vivo platelet activation. We also investigated the relationship between inflammatory markers and F2-isoprostane formation in this setting.

METHODS AND RESULTS

A cross-sectional study was performed in 23 insulin-treated patients aged <18 years with new-onset T1DM (<or=6 weeks, group A), matched for age and gender with 23 patients with stable disease (>1 year, group B). Urinary 8-iso-PGF2alpha and 11-dehydro-TXB2 were measured in all patients and in age- and gender-matched controls. Circulating interleukin-6 (IL-6), tumor necrosis factor-alpha, and C-reactive protein were also determined as markers of the inflammatory response. Fifteen of the 23 children in group A were reexamined after 12 months. Compared with either controls or group B, diabetic children in group A showed significantly higher levels of 8-iso-PGF2alpha, 11-dehydro-TXB2, IL-6, tumor necrosis factor-alpha, and C-reactive protein. Statistically significant correlations between IL-6 and both 8-iso-PGF2alpha (r=0.63, P<0.001) and 11-dehydro-TXB2 (r=0.51, P<0.01) were observed. The 15 patients reexamined after 1 year showed a significant reduction in lipid peroxidation and platelet activation (P<0.02 and P<0.001, respectively), consistent with reduced levels of IL-6 and tumor necrosis factor-alpha.

CONCLUSIONS

These results demonstrate that enhanced lipid peroxidation and platelet activation represent early events in T1DM that are possibly related to an acute inflammatory response. These noninvasive indexes may help in further examining T1DM pathophysiology and monitoring pharmacological interventions to interfere with disease development and progression.

Superoxide dismutase and oxidative stress in Dahl salt-sensitive and -resistant rats

The roles of oxidative stress and renal superoxide dismutase (SOD) levels and their association with renal damage were studied in Dahl salt-sensitive (S) and salt-resistant (R)/Rapp strain rats during changes in Na intake. After 3 wk of a high (8%)-Na diet in S rats, renal medullary Cu/Zn SOD was 56% lower and Mn SOD was 81% lower than in R high Na-fed rats. After 1, 2, and 3 wk of high Na, urinary excretion of F(2)-isoprostanes, an index of oxidative stress, was significantly greater in S rats compared with R rats. Plasma F(2)-isoprostane concentration increased in the 2-wk S high Na-fed group. After 3 wk, renal cortical and medullary superoxide production was significantly increased in Dahl S rats on high Na intake, and urinary protein excretion, an index of renal damage, was 273 +/- 32 mg/d in S high Na-fed rats and 35 +/- 4 mg/d in R high Na-fed rats (P < 0.05). In conclusion, salt-sensitive hypertension in the S rat is accompanied by marked decreases in renal medullary SOD and greater renal oxidative stress and renal damage than in R rats.

Biomarkers of oxidative damage in cigarette smokers: which biomarkers might reflect acute versus chronic oxidative stress?

Cigarette smoking predisposes to the development of multiple diseases involving oxidative damage. We measured a range of oxidative damage biomarkers to understand which differ between smokers and nonsmokers and if the levels of these biomarkers change further during the act of smoking itself. Despite overnight abstinence from smoking, smokers had higher levels of plasma total and esterified F(2)-isoprostanes, hydroxyeicosatetraenoic acid products (HETEs), F(4)-neuroprostanes, 7-ketocholesterol, and 24- and 27-hydroxycholesterol. Levels of urinary F(2)-isoprostanes, HETEs, and 8-hydroxy-2'-deoxyguanosine were also increased compared with age-matched nonsmokers. Several biomarkers (plasma free F(2)-isoprostanes, allantoin, and 7β-hydroxycholesterol and urinary F(2)-isoprostane metabolites) were not elevated. The smokers were then asked to smoke a cigarette; this acute smoking elevated plasma and urinary F(2)-isoprostanes, plasma allantoin, and certain cholesterol oxidation products compared to presmoking levels, but not plasma HETEs or urinary 8-hydroxy-2'-deoxyguanosine. Smokers showed differences in plasma fatty acid composition. Our findings confirm that certain oxidative damage biomarkers are elevated in smokers even after a period of abstinence from smoking, whereas these plus some others are elevated after acute smoking. Thus, different biomarkers do not measure identical aspects of oxidative stress.

Effect of high-dose alpha-tocopherol supplementation on biomarkers of oxidative stress and inflammation and carotid atherosclerosis in patients with coronary artery disease

BACKGROUND

Oxidative stress and inflammation are crucial in atherogenesis. alpha-Tocopherol is both an antioxidant and an antiinflammatory agent.

OBJECTIVE

We evaluated the effect of RRR-alpha-tocopherol supplementation on carotid atherosclerosis in patients with stable coronary artery disease (CAD) on drug therapy.

DESIGN

Randomized, controlled, double-blind trial compared RRR-alpha-tocopherol (1200 IU/d for 2 y) with placebo in 90 patients with CAD. Intimal medial thickness (IMT) of both carotid arteries was measured by high-resolution B-mode ultrasonography at 0, 1, 1.5, and 2 y. At 6-mo intervals, plasma alpha-tocopherol concentrations, C-reactive protein (CRP), LDL oxidation, monocyte function (superoxide anion release, cytokine release, and adhesion to endothelium), and urinary F(2)-isoprostanes were measured.

RESULTS

alpha-Tocopherol concentrations were significantly higher in the alpha-tocopherol group but not in the placebo group. High-sensitivity CRP concentrations were significantly lowered with alpha-tocopherol supplementation than with placebo (32%; P < 0.001). alpha-Tocopherol supplementation significantly reduced urinary F(2)-isoprostanes (P < 0.001) and monocyte superoxide anion and tumor necrosis factor release compared with baseline and placebo (P < 0.001). No significant difference was observed in the mean change in total carotid IMT in the placebo and alpha-tocopherol groups. In addition, no significant difference in cardiovascular events was observed (P = 0.21).

CONCLUSIONS

High-dose RRR-alpha-tocopherol supplementation in patients with CAD was safe and significantly reduced plasma biomarkers of oxidative stress and inflammation but had no significant effect on carotid IMT during 2 y.

Peripheral F2-isoprostanes and F4-neuroprostanes are not increased in Alzheimer's disease

Quantitative biomarkers of oxidative damage, such as the F(2)-isoprostanes (IsoPs) and F(4)-neuroprostanes (F(4)-NeuroPs), may be useful in assessing progression and response to therapeutics in patients with Alzheimer's disease. F(2)-IsoPs and F(4)-NeuroPs are reproducibly increased in brain and cerebrospinal fluid of Alzheimer's disease patients; however, results in blood and urine have been conflicting. We tested the hypothesis that F(2)-IsoPs and F(4)-NeuroPs in plasma or urine quantitatively reflect oxidative damage to the central nervous system. Our results showed that urine levels of F(2)-IsoPs or their major metabolite were not significantly different between 56 Alzheimer's disease patients and 34 controls. In addition, urine and cerebrospinal fluid F(2)-IsoP levels in 32 Alzheimer's disease patients did not correlate. Supporting these conclusions, elevated rat cerebral F(2)-IsoPs and F(4)-NeuroPs after systemic exposure to kainic acid were not associated with a significant change in their plasma or urine levels. These results show that plasma and urine F(2)-IsoPs and F(4)-NeuroPs do not accurately reflect central nervous system levels of these biomarkers and are not reproducibly elevated in body fluids outside of central nervous system in Alzheimer's disease patients. These results should guide the organization of clinical trials now being planned for patients with Alzheimer's disease.

Effects of oral glutathione supplementation on systemic oxidative stress biomarkers in human volunteers

BACKGROUND

The tripeptide glutathione (GSH) is the most abundant free radical scavenger synthesized endogenously in humans. Increasing mechanistic, clinical, and epidemiological evidence demonstrates that GSH status is significant in acute and chronic diseases. Despite ease of delivery, little controlled clinical research data exist evaluating the effects of oral GSH supplementation.

OBJECTIVES

The study objectives were to determine the effect of oral GSH supplementation on biomarkers of systemic oxidative stress in human volunteers.

DESIGN

This was a randomized, double-blind, placebo-controlled clinical trial.

SETTING/LOCATION

The study was conducted at Bastyr University Research Institute, Kenmore, WA and the Bastyr Center for Natural Health, Seattle, WA.

SUBJECTS

Forty (40) adult volunteers without acute or chronic disease participated in this study.

INTERVENTION

Oral GSH supplementation (500 mg twice daily) was given to the volunteers for 4 weeks.

OUTCOME MEASURES

Primary outcome measures included change in creatinine-standardized, urinary F2-isoprostanes (F2-isoP) and urinary 8-hydroxy-2'-deoxyguanosine (8-OHdG). Changes in erythrocyte GSH concentrations, including total reduced glutathione (GSH), oxidized glutathione (GSSG), and their ratio (GSH:GSSG) were also measured by tandem liquid chromatography/mass spectrometry. Analysis of variance was used to evaluate differences between groups.

RESULTS

There were no differences in oxidative stress biomarkers between treatment groups at baseline. Thirty-nine (39) participants completed the study per protocol. Changes in creatinine standardized F2-isoP (ng/mg creatinine) (0.0±0.1 versus 0.0±0.1, p=0.38) and 8-OHdG (μg/g creatinine) (-0.2±3.3 versus 1.0±3.2, p=0.27) were nonsignificant between groups at week 4. Total reduced, oxidized, and ratio measures of GSH status were also unchanged.

CONCLUSIONS

No significant changes were observed in biomarkers of oxidative stress, including glutathione status, in this clinical trial of oral glutathione supplementation in healthy adults.

Increased renal medullary H2O2 leads to hypertension

We have recently reported that exaggerated oxidative stress in the renal medulla due to superoxide dismutase inhibition resulted in a reduction of renal medullary blood flow and sustained hypertension. The present study tested the hypothesis that selective scavenging of O2*- in the renal medulla would prevent hypertension associated with this exaggerated oxidative stress. An indwelling, aortic catheter was implanted in nonnephrectomized Sprague-Dawley rats for daily measurement of arterial blood pressure, and a renal medullary interstitial catheter was implanted for continuous delivery of the superoxide dismutase inhibitor diethyldithiocarbamic acid (DETC, 7.5 mg x kg(-1) x d(-1)) and a chemical superoxide dismutase mimetic, 4-hydroxytetramethyl piperidine-1-oxyl (TEMPOL, 10 mg. kg-1. d-1). Renal medullary interstitial infusion of TEMPOL completely blocked DETC-induced accumulation of O2*- in the renal medulla, as measured by the conversion rate of dihydroethidium to ethidium in the dialysate and by urinary excretion of 8-isoprostanes. However, TEMPOL infusion failed to prevent DETC-induced hypertension, unless catalase (5 mg x kg(-1) d(-1)) was coinfused. Direct infusion of H2O2 into the renal medulla resulted in increases of mean arterial pressure from 115+/-2.5 to 131+/-2.1 mm Hg, which was similar to that observed in rats receiving the medullary infusion of both TEMPOL and DETC. The results indicate that sufficient catalase activity in the renal medulla is a prerequisite for the antihypertensive action of TEMPOL and that accumulated H2O2 in the renal medulla associated with exaggerated oxidative stress might have a hypertensive consequence.

Role of reactive oxygen species in endothelin-induced hypertension

Recent reports have indicated that endothelin-induced vasoconstriction in isolated aortic vascular rings may be mediated by the production of superoxide anion. The purpose of this study was to determine the role of superoxide anion in mediating the chronic renal and hypertensive actions of endothelin. Endothelin-1 (5 pmol/kg per minute) was chronically infused into the jugular vein by use of mini-osmotic pump for 9 days in male Sprague-Dawley rats and in rats treated with the superoxide anion scavenger tempol (30 mg/kg per day). Mean arterial pressure in the endothelin-1-treated rats was 141+/-3 mm Hg, compared with 125+/-2 mm Hg in control rats. Endothelin-1 increased renal vascular resistance (15.3+/-2.5 versus 10+/-1.3 mm Hg/mL per minute) and decreased renal plasma flow (6.5+/-0.9 versus 8.7+/-0.7 mL/min) in control rats. Endothelin-1 also significantly increased TBARS in the kidney and urinary 8-isoprostaglandin F2alpha excretion. The increase in arterial pressure in response to endothelin-1 was completely abolished by tempol (127+/-4 versus 127+/-4 mm Hg). Tempol also markedly attenuated the renal plasma flow and renal vascular resistance response to endothelin-1. Tempol also significantly decreased the level of 8-isoprostaglandin F2alpha in the endothelin-1-treated rats. Tempol had no effect on arterial pressure or renal hemodynamics in control rats. These data indicate that formation of reactive oxygen species may play an important role in mediating hypertension induced by chronic elevations in endothelin.